Your hardware address will look something like this: 00:00:01:02:A0:AB
It will be 12 characters long, split into 6 groups of two.
Windows 95/98/ME
Go to the Start menu
Click on Run
Enter the word command and click ok
Inside the Command Prompt Window and type the command winipcfg /all | more
In the Ethernet Adapter Local Area Connection: area, look for the Physical Address .......: line with a 12 character entry. Those 12 characters are the value you want.
Windows NT/2000/XP
Go to the Start menu
Click on Run
Enter cmd and click ok
When the window pops up, type ipconfig /all and hit enter Look for the item that saysPhysical Address............ The corresponding 12 characters are what you want.
Mac OS 9.x
Click on the Apple Icon in the upper left corner of your screen
Select the Apple System Profiler
Under the System Profile tab, expand the Network Overview entry
Next, expand the Apple Talk entry. The 12 digit value labeled as Hardware Address is what you want.
Mac OS X
Click on the Apple Icon in the upper left corner
Select System Preferences
In the system preferences, select the network panel In that panel you will see the 12 digit hardware (MAC) address
Unix
Open a terminal window and type the command: ifconfig -a.